Resistance Brazing

Resistance brazing is yet another vital process of brazing. It is actually the production of bonding which happens due to the obtainment of the heat from resistance to the flow of electric current in a circuit of which the workpiece is a part. By making use of a nonferrous filler metal with a melting point above 427°C (800°F), the metal is distributed in the joint by capillary attraction.

The Process of Applying Resistance Brazing
The resistance brazing process do follow a particular methodology. The filler metal in the form of shims which needs to be brazed are preplaced amidst two overlapped workpieces to be joined. By making use of a standard spot or projection welding machine, the assembly is brazed. Later the heat is obtained when electric current is passed through the workpieces using contacting water cooled electrodes. These electrodes are placed on every single side of the area which are to be heated as in spot or projection welding. Resistance brazing demands lower pressure and longer time of current flow.

Usually, carbon alloys or carbon electrodes are used for making contacting electrodes. Heat is developed in carbon alloys within the work since the base metal and filler metal resist towards the flow of (low voltage) high current through the work. While in case of carbon electrodes, heating is produced within the carbon due to the high resistance of carbon & it is then conducted to the work. Keeping this in mind, the application of Wand Mo electrodes are generally preferred to carbon electrodes simply because they possess longer life withstanding any high unit pressure.

Resistance Brazing vs Resistance Welding
As we know, resistance welding is actually a group of welding processes in which heat obtained from the resistance of the work piece to electric current in a circuit leads to the production of coalescence. The workpiece is just a part of this this electric current & by applying pressure, the necessary heat is obtained.

With that in mind, there is a considerable difference between two confusing processes, i.e. Resistance brazing & Resistance welding. In resistance brazing, the low melting metal needed to be brazed is placed between the two surfaces.

Advantages
The plus points of resistance brazing are a handful which have been described below :

• Cheap & demands less skill from labors
• Provides controlled & rapid localized heating
• Lessens fire hazards
• Yields high production rate

Limitations
Though, not much disadvantages are there, some of the vital ones have been highlighted as :

• Both side accessing of the joint should be possible
• Has distortion problem
• Simultaneous brazing of components not possible, one at a time making it tedious

Applications
Resistance brazing have a number of vital applications which proves the worth of this brazing method.

• Extensive usage in case of small areas (small parts) to be brazed.
  
  
• Copper 7 copper alloys are the two most often work metals by this method using silver and phosphorus copper brazing alloys.
  
  
• Easily joins assemblies assorted having joint areas of about 62.5 to 94 sq. cm with wires 0.025 to 0.125 mm in diameter.